A fourth U.S. soldier was killed along with three Army Green Berets during a mission this week in Niger, West Africa, according to U.S. Africa Command.

The soldiers were on a reconnaissance patrol as part of what the command described as an advise-and-assist mission with Nigerien forces on Wednesday when they were ambushed by an enemy the command declined to identify. A two-day search-and-rescue effort located the body of the fourth soldier.